I can’t open Google docs so I cannot see your itinerary, but I assume it includes the Victoria and Albert, and the Design Museum.
https://designmuseum.org/
You will need advance tickets to see the special exhibits at this museum (“The World of Tim Button” and “Barbie”), but the rest is free.
For nighttime activities, I suggest a ride on the Thames Clipper boats to see the Illuminated River fart installation:
https://illuminatedriver.london/
In theory, they offer special tours with narration each Saturday evening, but do not list a current schedule for that. They do offer photography courses on two Wednesdays in December. But you can also just use the boats for a ride up or downriver on their regular commuter service. It is a great way to move east-west around London. can see the regular daily and weekend schedule and routes here:
https://www.thamesclippers.com/commuters/commute-by-river
As for vegan dining, London may be one of the best places in the world for variety. Lots of the Indian restaurants offer vegan dishes, but also check menus on gastropubs. The Ivy restaurants usually have a vegan/vegetarian menu and there are several scattered around London:
https://ivy-menus-2.theloyaltyco.app/wp-content/uploads/2024/11/10738_TIC_Christmas_2024_Premium-P4_ISC_Vegan_WEB.pdf
For something upscale and creative, try Ottolenghi’s Rovi, an all-vegetable restaurant:
https://ottolenghi.co.uk/pages/locations/rovi
https://cdn.shopify.com/s/files/1/0557/6651/5815/files/OTL51-A4-Rovi_ALC-Menu-Oct24_2_0a32fcc0-e20d-44e2-9328-44848d7130c7.pdf?v=1730730921